Gas mixing apparatus



Jime'30, 1931. E. o. ENG EL S GA MIXING APPARATUS Filed 001;. 27, 1925 7 Sheets-Sheet l ATTORNEY June 30, 1931.

Pic. 2.

GAS MIXING APPARATUS F iled Oct 27, 1925 E. o. 'ENGELS 7 Sheets-Sheet 2 Y I r ATTORN YS June 30; 1931. E. o. ENGELS GAS MIXING APPARATUS Filed 001;.

1926 7 Sheets-Sheet 5 INVENTOR 'EUGE/VE O. E/VGELS ATTO R N Y5 June 30, 1931. E, c5, ENGEL 1,812,089

GAS MIXING APPARATUS Fild oct. 2'7, 1926 7 Sheets-Sheet 4 INVENTOR 51/65/750. F/VGELS June'30, 1931. E. o. ENGELS ,8

. 'GIAS MIXING APPARATUS Filed Oct. 27, 1926 7 Sheets-Sheet s INVENTOR 500.9% 0. E/VGELS AT ORNEY5 June Q. ENGELS GAS MIXING APPARATUS File O t- 1926' 7 Sheets-Sheet 6 IN VENT OR El/Gf/VE 0. E/VGELS BY /,l I

ATTORNEYS June 30, 1931. E. o. ENGELS 1,812,089

GAS MIXING APPARATUS Fi e oct- 27. 1926 1 Sh eets-Sheet 7 FIG. 10.

I 5 4e I 75 45 In? 4e 45 a5 97 26 17 m T 2"? M 2a 3/ I00 3? l I I 32 IO 27 v 52L; 98 7 Patented June 30,- 1931 EUGENE OSCA-RENGELS, or sAGINAwr/rroHmAn, assrenon'ro BAxER'PERxm scoM IPA1\TY,. OE'SAGINAW, MICHIGAN, A CORPORATION 01? NEW YORK GAS MIxiNe'ArPARA'r s Applicatioii fil ed October 27(1'92'6. seii arna miwa y This invention'relates to gas mixing rappara'tus'for gas .firing systems. I Certain features o f'the invention relate particularly to gas firing" systems including 5 a gas mixing'appar'atus 'in whic'h' the-quantity of' the gasesentering'themixing appratus controlled by the pressure prevailing in the produced gas mixture, the quantity ofthejgases suppliedbeing decreased When 10 thispressure rises and increased when said pressure falls; A a v V I This invention is particularly applicable to gas firing systems for heating baking ovens, drying rooms and the like inlwhich a gaseous mixture'is burned "in theoven chambers by means of openfflame burners. Itis'evident that the atmosphere in such ovens contains little or no oxygen so that the fuel gas must be'ilnixe'd with a sufficient V quantity of oxygen or air for proper com-- bustio'n before being 'fed'tQ the burners. It

isimportant in such systems thatthepropor gasvand air be maintained at a tion of fuel a valuejsuch that "at all timesthe gaseous mixfor its efficient combustion, and it-is there fore highly important" in gas' firing systems that themixing apparatus shall-be capable of use Withvarious kind'so-f fuel gas. Pro ducer gas requires substantially an equalratus of the character jabove described'in which the apparatus may be. quicklyfand tu're may be burned at a maximum; efficiency. v a In'gas firing-plants, it'is frequently ne'ces sary or desirable to change the fuel gas beart. ing 'used inth'emiXture for another gas ref H quiringa'different quantitytofair or oxygen-r easilyregulated to produce mixtures of "dif- V ferent proportions "of gasesrequired for effi cient combustion. V

Another object of the invention is to provide a gas mixing apparatus constructed and arranged to mix gases for the formation of a"combust1ble' m xture; 1n certain definite proportions in which the proportion of the gasesfin the-mixture may bez'readily varied ra't'usf" r a, r

Another object ofthe' invention is to proas desired during the operationof the appai videa' gas mixii'ig apparatushaving pro visionfor' controlling the quantity of the gases entering the mixing apparatus in ac cordance With "the a pressure existing in the efficient combustible mixtureiv a, I With theseand othergobjectsfin view the invention comprises i certain novel i and im' proved features,.1c'0nstructionsandcoinbinm r tions ofiparts hereinafter described. and i o particularly 'pointed out in the 'claiins, the

a dvantag es'of which" ill'befreadily under) I stood and appreciated I th'oseyskilled the v Y o The inventionwvill clearly understood from the accompanying drawings illu'strat 5 ing the' inv'ention in itsfpreferred 'fo 'r'm'jand a f produced gas mizrture'in which the proper-ff tion of the gases 1n the mixture'formed may a be varied as j desired to produce thefm'ost the following detaileddescriptionjof the con i struction" therein-shown.- Infthe drawings Fig'. l is verticalisection through the center'ofa mlxmgapparatusbuilt 1n acoordance with this invention; o,

" Fig. 2is "a horizontalsection taken on showing the control {mechanism and external connections;

'Fig; 6 is a vertical section taken longi tudinally through theicentenof the mixing apparatus and at right angles to the section i of Figlv 1;

sectionjtaken n the tri 3 ispa; vertical ec ion 'jtakenfon the so I ' 'F'ig 'f5 is a' p'l'anview olf theapparatus 7 1 eat. elevationfof thef a ps ratusshowing'*insection'a;pressurecylinder 1,

for automatically controlling the supply of gases;

Fig. 8 is a side elevation of a portion of the mechanism shown in Fig. 7;

Fig. 9 is a sectional view showing a modilied form of the invention;

Fig. 10 is a section taken on the line 2 1010 of Fig. 9; and

Fig. 11 is a perspective view showing the internal construction of the form of apparatus shown in Figs. 1 to 9 inclusive.

For the most eiiicient operation of gas firing plants, it is desirable to maintain the pressure of the gaseous mixture at the burners as nearly constant as possible, and to this end the flow of gases into the mixing apparatus is suitably controlled in the present construction. In actual practice, the total consumption of by the burners is always varying because individual burners are turned on and off and up and down constantly during the operation of the system. Variation in consumption, of course, varies the pressure in the lines supplying the burners and unless the supply of gas to the lines is controlled in accordance with this pressure, the burner flames flicker and become irregular. For this reason, in the present construction the pressure in the supply lines is employed to control automatically the quantity of gases admitted to the mixing chamber as the pressure varies, the quantity of these gases being increased when the pressure in the main supply line diminishes and the quantity of the gases being diminished when this pressure increases.

In order to mix fuel gas and air in the proportions desirable for forming a combustible mixture in the present form of the invention, the apparatus is provided with a main housing 11, preferably cylindrical in cross-section, having one end closed, as by a cover 16, and the other end opening, by means of outlet 15, into a main 53, which supplies the burners with the combustible mixture. Fuel gas and air preferably are led into the housing 11 through inlets 12 and 13 arranged in the cylindrical wall of the housing diametrically opposite to each other.

Fitting tightly to the inner walls of housing 11 and extending longitudinally from its closed end, well past the inlets 12 and 13, is a cylindrical proportioning tube 17 having a flange 19 which is rigidly secured between flange 18 of housing 11 and flange 20 of cover 16 by means of bolts 21. Gas and air are admitted into the mixing chamber 14 only through sets of preferably equal sized and parallel slot-like ports referred to collectively as 22 and 23 cut in the opposite walls of the cylindrical tube 17. Ports 22 are arranged in the tube 17 so that the fuel gas which enters through inlet 12 passes through forechamber 24. formed in the side of housing 11 and then through the ports 22 into the mixing chamber. Ports 23 similarly are located so that air entering forechamber 25 from inlet 13 passes through ports 23 into the mixing chamber.

In order to regulate the amount of gas admitted into the mixing chamber 14, a cylindrical valve tube 26 is mounted for axial sliding movement and for rotative movement within the proportioning tube 17. The valve 26 is provided at one end with radial arms 27, connected to a central sleeve 29, and at its opposite end with radial arms 28, connected with a central sleeve 30 and a valve actuating rod 32 is secured by means of pins 31 within the sleeves 29 and 30. The rod 32 passes through a stuiiing box 33 in the cover 16 and terminates in a knob or handle 36 by which the rod and valve tube may be actuated manually.

The valve tube 26 in the preferred construction is provided with two openings, one indicated at 34, preferably having its length and width at least equal to the corresponding dimensions of that portion of tube 17 in which the slots 22 are formed. The other opening in the valve tube indicated at 35 has a width preferably at least equal to the length of the slots 23 and extends nearly the full length of the valve tube, as clearly shown in Figure 2. When the valve tube is slid inwardly from the position shown in Figure 2 by an actuation of the adjusting rod 32, the ports 22 will be closed successively by the solid portion on the tube 26 to the right of the opening 341:. The ports 23 however, Will continuously remain open. Thus by the axial adjustment of the valve tube, the proportion of fuel gas admitted through the ports 22 to the air admitted through the ports 23 will be altered. By a rotation of the valve tube from the position shown in Fig. 1 in the direction of the arrow, the ports 22 and 23 will be closed to an equal degree but the proportion of fuel gas and air entering the valve chamber through the respective ports 22 and 23 will remain unchanged. The quantities of these gases entering the mixing chamber will, however, be diminished in accordance with the extent to which the valve tube is rotated. It is evident that both of these adjustments may be made simultaneously if desired.

The extension of rod 32 outside the valve casing has been calibrated in such a manner that it is possible to ascertain by merely glancing at the location of an indicator 37 what fuel gas ports 22 have been closed. For this purpose, marks a to f are cut or stenciled in rod 32 in such relation that when indicator 37 points to mark a, port a is closed and when it points to Z), ports a an d b are closed, and so on until when mark f is reached all of the ports are closed and no gas is being supplied. If desired, the calirsiego'so j brations" on' -rod 32 may be made directly 1 to indicate the-adjustment of the valve tube forithe ty 'eof fuel;gas'-emp1oyed,' such as 7) rodv32, the operator :may easily and quickly set the mixing device for supplying various kinds' of gases requiringdifierentamounts of air for the most efficient combustion oft he mixture. p p As above stated when the'pressure of the gaseous mixture in the .supply mains is at,

- a predetermined value, the pressure on the underside of the diaphragm, which is the same as the pressure in the supply'm'ain, and

the'downward force of the weight v'72 balance each other. I This weight, therefore,: determines the normal pressure inthe supply main and this normal pressure may be.var-

ied by the substitution of'diflerentfweightsj It is desirable to: maintain asnearlya unifo rmyflow of the gaseous mixture to the side. of diaphragm A? through Yvents 52: in cover 48. Thisdiaphragm 47- is freeto-move phragm 47,

'wardly. p v I .;{A disc v57 is rigidly fixed tothe central r rod --6l is arranged to actuate the, plunger 1 62 of a valve 50 slidably mounted in a suit-E able housingiiiormed by-the boss 49; Upward movement of the rod v61 in the guideway 69-is limited by the engagement of theupper burners as possible and itis therefore desir' able tozprevent violent; fluctuationsin the pressure of the 'gaseous mixture in the main by which the burners: are supplied. This is best accomplished by automatically regulatingthe quantity of gas and air admitted into the; .mixing chamber in accordance with fluctuations in the supply line pressure.

I For this purposerpreferably a branch pipe linebihaving aregulating valve connects the supply main" 53. with the lower portion of a .chamber46 for med'by an an- 'nularp'rojectio'm5L5 on housing ll. ".The pressure ofthe gaseous mixture inchamber 46 which is thesame as thatin the'supply. main,-,acts. upon. a diaphragm :47 stretchedby means -.of set screws .51 across the top of chamber 46 between. the annular projec tion 45 and-a vaulted cover Atmospheric pressure: is maintained on the upper up and :down at its gcentre. 'Whenever' the pressure. in the chamber 46 rises sufliciently to overcome the atmospheric pressure and'the I weight lot the partssupported bythe. dia+ said diaphragm is moved *uppart of the diaphragm 47 and/carries alslide rod61 arranged to slide in a suitable guide;

way} 69 formedin a boss 49 projecting centrally from the vaulted cover 48. This slide end ofanenlargeme'nt63 011113116 rod with the upper face of} acrecess 68'insthe boss 7 49in which said enlargement engages. -The boss 49- is formed also with receive the disc157.

i natural or -oil gas? Thusby a simple longitudinal movement of recess 67 te' A'central 56 is secured to the lower side of the diaphragm and to this disc. is

attached a short guide rod 58 engaging ina guidew'ay 59, passing centrally through a projection 60 on the framev below the dia-'" phragm. The downward movement ofthediaphragm is limited bytheengagement of the disc 56 with the upper end of the r jecti'on 60, Y r v The'va'lve 50in the preferred construction is provided "with a peripheral groove'6 l',

which when-the valve is in a certain-po'sition in, its housing connects the passageways I 73 and 74 formed in the boss 49; The pas sageway 73 communicates with a pipellinef 7 5 leading from the air inlet 13.- The'passage'way 74; is connected by a pipe line *76 with an air pressure cylinder 77, in which] is slidably mounted a piston 78, the pipe.

line communicating with the cylinder at a point above the piston inall positions-of I the piston (see Figure Whenthe valve 7' 50i's in position to establish communication between the passageways 73 and 74, air un- .der pressure is led from theinlet-18 through said passageways and. pipe line 7 6" into pressure cylinder hingedclasp '91 surrounding the cylinder;

and securely" held thereon by bolt 93. The

-members of hinged clasp 9l are Secured by bolts @2110 an arm 88 on a bracket 86' attache'dlto the frame or the apparatus. In-

Thisv cylinder is mounted atits base upon a bracket 87 havinganupturned rim 9%} and attachedfto the frame of the apparatus, and the cylinder is heldiin' i position on said bracket by means} of. ai

stead-of takingfor-the above purpose air under pressure from 'the'inlet '13, anysuitable gaseous fluid under suitable pressure 4 I p i io's I 11 move downwardly u'n- I p der the pressureof the air entering on its;

"upper side and will-carryFwithitdink rod may be employed;

Th'episton 78 -w1 79, which is hingedly connected to piston 7 8 at' one 'e'nd,jand at the other end is pivotally to rod32 of? valve tube 26} Valve tube-26 is' thus rotated in a direction to close pan ti'all-y or "to close to a further degree the air of thumb-screw 83 for the purpose ot bal The cylinder 77 is formed at its lower end with a slot and-thebracket 87 is formed witha-slot 96 in which the lever8O and link.

bar 79operate. fAs-soon. asthe-qu'antity of gases:admittednthrough ports '22 and 23 is 1 reduced as a result of their partial" closing, the ipressui-exexisting :tinimain 53. will be' re 9 connected to one arm of a two-armed lever '80 Whi'ch'-*- is-rigidly secured at itsiniddle part by means of sleeve 81 and set screw 84 duced, whereupon the pressure on the urn der side of diaphragm 17 is diminished. The latter then moves downward under the pressure of weight 72, carrying with it the plunger 62 of valve 50.

The valve 50 is also formed with a pcripheral groove 65, somewhat wider than the groove G l and so arranged that, when the valve is in a certain position in its housing, the groove connects the passageway 74 with a passageway 85 in the boss 4-9, leading from the valve housing to the outside at mosphere. It will be noted from an inspection of Figures l and G that the passageway 85 is in a plane somewhat higher than the passageways 78 and 74. The valve 50 is acted upon by the veiglit 72 mounted on an extension on the valve plunger and engaging at its base a supporting disc "Tl on the plunger, which weight tends to hold the valve in its lowermost position in the hous in hen the gaseous mixture in the supply main 53 is under a i iredetermined normal pressure, the gaseous pressure on the unerside of the diaphragm 47 balances ti o rce or the weight 72 and the valve 55) is maintained in a position in the valve housin cut off communication between the passag ways 73 and 74 and also to cut off communication between 11 assageway 7a and passageway 85. The valve tube 26 under ordinary conditions when the normal predetermined pressure exists in the supply main will oc cupy a position about its oi rotation to close partially both the ports 23 through which the air enters the mixing chamber and the ports 22 through which the fuel enters said chamber, in accordance with the amount of gas mixture consumed by the burners.

\Vhen the pressure in the supply main tails below this predetermined pressure, on account of the turning on or the turning up of one or more burners, or for any other reason, diaphragm 4-7 is depressed and the valve 50 is moved downwardly by the weight 72. The downward movement of the valve brings the groove (55 into position to connect the passageway 7a with the passageway 85, thereby allowing the cylinder 77 to exhaust gradually into'the atmosphere and the piston 7 8 is slowly moved upwardly in the cylinder 77 by the action of the weight 82. Thus, the valve tube 26 is adjusted to open further the ports 22 and 23, allowing an increased supply oi air and fuel gas to enter the mixing chamber. This will increase the pressure of the gaseous mixture in the supply main and the diaphragm will rise, carrying the valve 5-0 upwardly until, when substantially the normal pressure is reached in the supply main, groove 65 is carried outot registration with passageway 74, thereby cutting off communication between passageweight 72, thereby bringing groove 64L into registration with passageways 74 and 73. When this occurs, compressed air from the inlet 13 will enter the upward part of the cylinder 77 thereby moving the piston 78 downwardly in the cylinder. This downward movement of the piston will actuate the valve tube 26 to close further the ports 22 and 23, thereby diminishing the supply of air and fuel gas entering the mixing chamber. This wi diminish the pressure of the gaseous mixture in the supply main and the diaphragm 47 will fall and the valve 50 will move downwardly under the force of the w ht 72 until, when substantially the normal pressure reached in the supply main, groove 64: is carried out of registration with pa igeways 73 and 7 4 and communicaties between these passageways is cut off by the valve.

Thus valve tube 26 is automatically adjusted in accordance with the pressure in supply main to supply ust the amount of and air required for the burners. The grooves 64 and 65 are preferably made substantially in the form in the drawings; that is, the groove 64 is made somewhat shorter than the groove 65 and tapers toward its upper end, while groove (35 tapers toward its lower end. In actual practice it has been found that these forms of grooves are most eflicient in the operation of the valve mechanism.

The present construction enables a change to be made from one kind of fuel gas to another quickly and easily during the operation of the system. H, during the operation of the present apparatus, a supply of one lrind of fuel gas is exhausted and it is desired to substitute another kind of fuel gas available for use, which requires a different proportion of air for its complete and efficient combustion, it is only necessary to loosen the screw 84 and then to slide the rod 32 either inwardly or outwardly to the proper setting for the gas to be used, as indicated by pointer 37. Screw 84 may then be tightened in the desired position and the substituted gas admitted through the same inlet as the former gas.

Producer gas requires for its complete combustion about an equal volume of air. For other gases ordinarily employed in gas firing systems, such as town gas, natural gas or oil gas, five or six volumes of air are ordinarily required for one volume of fuel gas to produce complete and efficient combustion. The proportioning and mixing valve disnmaose closed -:in:F-igures' -1- 6o 8; inclusivasand Fig: ure 1'1 is-intended particularly for use. with producer gas in asystem in which, when-the: producer gas-is exhausted, aichange' is madetotown gas, natural gas or; oil gas; In .the

construction shown in these figures, the' proportionofi fuel:gasfo air'anthe mixture is produced byivaryingfionly the quantity, of fuel gas. Whenever the types of fuelgas availablefor use in a gas firingsystem are such that 1 the variations in their: airrre'quirements is small a as, for instance, f town} gas,

natural gas and oil gas, ltz may be advisable to; :vary; the proportions or: air and fuel gas in-I the mixture for the particular fuelgas used by varying ithe quantity of air admitted, whilekeepingtheamount of gas a substantially: constant factor of: the. 'proportiOn'J- Figures 9 and 10on the drawings disclose a; construction especially adapted. for

the usevinterchangeably with town gas,v.nate urahgas or oil: gas: [In-the 'constructlon shown -in-these figures, the gas inlet 97 is made 'considerably smaller and with acorrespondingly smaller forechamber: 98 than 1 in the construction': shown in Figures 1' to -8 in-.

elusive and Figure'i lli- The:-proportioning tube 1.7! contains on'ly oneport 99-for the admission of gas, while thegport's'i for the admission. of a-irgare dividedinto groups of difierent sizes.

wider thanany of the other ports and are One group of ports 101 are never closed by longitudinalgmovement of the valve tube'26. These wide ports 101 are q i of a size to admit the smallest relative quantity of air required for the complete and eflicient combustion of the quantity of fuel gasentering the mixing chamber through the port 99 by any of the fuel gases employed} I The proportioning tube. 17 is also formed with a second set or group of ports 102, preferably greater innumber than the ports 101 and smaller in size. In the con struction shown, the ports 102 are of sub-. stantially the same length as the ports- 101 but are considerably narrower than the. latter ports".

The valve tube 26 in the construction shown in Figures 9'and 10 is mounted within the proportioning tube in substantially the 7 same manner as in theconstruction shown 7 1n Flgures 1 to 8 inclusive and F1gure11 and has a similar construction. This valve tube, however, 1s provided withan enlongated opening 103 through which the fuel'.

gas passing through slot 99 enters the mixing chamber. The opening 103 .is of such a length that the port 99 is not closed by the valve tube during the movement of said tube longitudinally between its limiting positions. The valve tube 26 is, also provided with'an opening 10 1' through which the air passing throughthe ports 101'and 102 enters the mixing chamber. Thisopening is so arranged and is of such asize that the ports 10,21 will-beclosed successively by the longit u'di'na'l movement of the valve tube 26 to-' p ward the left fromethe position; in .which it up orts isshown in Figure 10 butth-at the l0l r'ema inopen' at alltimesl a WV'hcn the airports are all open, the greatthe: quantity of gas during, the operation of the device. on; accor'u-1txof5- the relatively largenumber. and narrow-ness of the ports 7 102, arelatively finead ustment of the rela tive quantity or. air maybe secured.

. As the: above described construction of'my i new gas mixer shows,-,its:working parts-and especially also those contained wlthln the mixer housing can beqeasilyand efficiently lubricatedand taken apartfor cleaning pur v i poses, which constitutes a great advantage,

It isto be understood that. the: invention is not; limited to the particular construction and arrangement of parts ofthe. illustrated embodiment of-the inventiombut that the invention be embodiedin othenforms l 0 within the 'scop e-ofrthe; claims.

VJhat I claim as new is:

1"; A. gas mixing apparatus, pomprisingqin combination agas -rec'eiving chamber, fmeans for supplying two -or more gases-in prede-f termined proportions. to the chamber, a valve for. adj usting; the ,quality; I of-ataleastconeof saidgases admitted, to; thef chamber, and

means for adj ustingthe valve in accordance with the. pressure ofthe gaseous; mixture, 3 o comprising,a cyllnder,.a-piston mounted 1n,

thecylinder, .a: connection between the, pisi eof 5 ton and" valve for adjusting thevalve, a

pipe gleading intothe said cylinder,' fluid under pressure. for v operating'jthe piston therein,.and a valve adapted to-control the flow of the I fluid under pressure into androut.

of the saidfoy linderand actuated byfthe' pressure of the: produced; gaseous ,mixture.

2.; r mixing apparatus. comprising {in I combinat on/ages m1x1'ng .chamber ,means for supplyingvtwo or more gases in.- predetermined proportions to. the chamber, said chamber. having. a cylindrical interior wall,

ports inv said ,wall, a; cylindrical tubular-' valve mounted within the cylindrical wall of said chamber for axialand rotative move-' 'mentito: adjust the area ofsaid'ports, means for automaticaly adjusting. the, valve rotatlvelywll l accor ance vvith thezipressure of the gaseous mixture, .comprising a cylinder,

apiston. mountedinlthe; cylinder, a v connect-ion between the: piston and, thewvalve for ,adjustingith'e, valve, a; pipe leadinginto the said. cylinder fluidlunder pressure for operating the piston therein, and lla'fvalve Q aerate. wheelie 1 W 9 the scanner iii-0 pressure into and out of the said cylinder and actuated by the pressure of the produced gaseous mixture and means for axially adjusting the valve. 7

3. In a gas firing system; a gas mixing apparatus comprising a mixing chamber provided with separate port-s through which the respective gases to be mixed may be passed into said chamber, and a single cylindrical Valve member movable longitudinally of said chamber independently of rotation to vary the effective area of one of said ports and thereby to vary the proportions of the gases admitted to said chamber and rotatable independently of its longitudinal movement to vary the effective area of the openings for each of' said, gases admitted to said chamber while maintaining the proportions thereof constant.

l. In a gas firing system a gas-mixing apparatus comprising gas-mixing chamber having a cylindrical wall, separate ports located circumferentially around said cylindrical wall for the entrance of the gases to be mixed, a cylindrical tube mounted in said chamber for axial and rotative movement, said tube being provided with apertures, one of which is of substantially the same size as one of said ports and another of which is of substantially the same circumferential width as another of said ports but exceeding that port in length, and means for moving said cylindrical tube parallel to its axis in dependent of its rotation so as to vary the effective area of one of said ports without varying the effective area of the other of said ports, and means for rotating said cylindrical tube about its axis independent of its longitudinal movement so as to vary the effective area of each of said ports proportionately.

5. In a gas firing system a gas-mixing apparatus comprising a gas-mixing chamber having a cylindrical wall provided with circumferential slots arranged in longitudinal rows along said cylindrical wall for admitting gases to said chamber, a cylindrical tube mounted in said chamber for axial and rotative movement, said tube being provided with apertures, one of which is of substantially the same size as the slotted area through which one of said gases is admitted to such chamber and another of said apertures being of a size such that two sides thereof substantially correspond with and are of substantially equal length with two sides of the slotted area for admitting another of said gases and the other two sides thereof substantially correspond with the other two sides of the slotted area except that they are greater in length than those of said slotted area, means for moving said cylindrical tube in a direction along said longer sides so as to vary the width of a slot or the number of slots through which gas is admitted to said chamber from one of said slotted areas, and means responsive to consumption of the mixture of gases for automatically moving said tube in a direction along the equal sides so as to vary the quantity of the gases admitted to said chamber through said slots without substantially changing the proportion of their effective openings.

6. In a gas firing system a gas mixing device comprising a chamber provided with inlet ports through which respectively the gases to be mixed are admitted to said chamber and a single valve member for controlling the passage of one or more of the gases into said chamber, said member being movable in one direction to vary the effective area of one or more of said ports while maintaining the efiective area of one or more of the remaining ports constant so as to vary the proportions of the gases admitted to said chamber and being independently movable in another direction to vary the effective area of each of said ports proportionately so as to vary the quantity of gases admitted to said chamber while maintaining the proportions thereof constant.

Signed at Saginaw, Michigan, this 20th day of October, 1926.

EUGENE OSCAR ENGELS. 

